Recently, there have been started operations of an MBMS (Multimedia Broadcast and Multicast Service) which simultaneously distributes multimedia data such as broadcast data to a plurality of user terminals. The specifications of the MBMS are established on the premise of use in a radio access network adopting a WCDMA (Wideband Code Division Multiple Access) method. Specifically, a plurality of radio base stations forming the radio access network transmit the same multimedia data thorough an SCCPCH (Secondary Common Control Physical Channel).
On the other hand, each of the user terminals obtains a combined gain of radio signals respectively received from adjacent radio base stations through the SCCPCH to improve reception quality of the multimedia data. In order to obtain the combined gain, timings of transmission through the SCCPCH need to be synchronized within a predetermined time difference between the adjacent radio base stations.
Therefore, in the radio access network, a radio base station controlling device (RNC: Radio Network Controller) adjusts (controls) the timings of transmission through the SCCPCH between the adjacent radio base stations.
Note that Patent Literature 1 discloses a method where a plurality of radio base stations are connected through an exclusive cable, and data for synchronization is transmitted and received through the exclusive cable, thereby synchronizing transmission timings of data between the radio base stations.